Advertisement

Advertisement

Salt-buster drug cuts sodium absorbed from food

People who need to reduce their salt intake may one day be able to take a drug that decreases the amount they absorb from food. The leftover salt is excreted in their faeces.

Most people have too much salt in their diet&colon; the average intake in the UK is 9 grams a day, while the recommended level is 6 grams. People with conditions such as kidney disease and heart failure are advised to aim for even lower levels. But this can be hard as the white stuff is found in many foods, such as bread, biscuits and breakfast cereals.

The drug, called tenapanor, is in early-stage clinical trials for people with severe kidney disease. But in theory it could also help people with other conditions stick to a low sodium diet, says Dominique Charmot of Ardelyx, the California-based company that developed it.

Advertisement

Tenapanor works by inhibiting a molecule in cells in the intestinal wall that transports sodium from the gut into the body. In 60 healthy volunteers, the drug cut sodium levels in urine – a measure of how much sodium is absorbed from food – by up to a third. It raised sodium in their faeces by similar amounts.

Reducing salt intake by a third would help people with kidney disease who aren’t supposed to eat more than 5 grams of salt a day, says Charmot. “The less salt you take in, the better you are.”

Water retention

The approach has parallels with a popular weight-loss drug. Orlistat, marketed under the name Alli or Xenical, blocks the absorption of fat in the gut. Orlistat does have an unpleasant side effect though&colon; the extra fat that is excreted can lead to oily diarrhoea and incontinence.

In the trial with healthy volunteers, tenapanor also caused slightly looser and more frequent bowel movements, although Charmot says that the stool consistency ratings stayed “within the normal range”. Because of this effect, the drug is also being tested as a treatment for constipation in people with irritable bowel syndrome.

In principle, since it works solely within the bowel and isn’t absorbed into the bloodstream, tenapanor is unlikely to affect other bodily systems. But this won’t become clear until the results from larger trials are in.

Graham MacGregor of the Wolfson Institute of Preventative Medicine in London, who heads the campaign group Consensus Action on Salt & Health, says that while the drug is some years away from use, it has potential. “It’s an interesting concept,” he says. But he believes it would make more sense for people to change their diets&colon; “Why eat all this salt and take a drug to block it?”

But Charmot disagrees. “It’s not a way to cheat,” he says. “It’s a way to help people comply with very strict sodium [targets]. It’s rare people can achieve that.”